190 lines
5.4 KiB
HTML
190 lines
5.4 KiB
HTML
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Copyright (c) 2017 Rodolfo Forte
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<!DOCTYPE html>
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<title>Design Patterns - Abstract Factory Presentation</title>
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class: center, middle
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# Abstract Factory
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---
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# Also known as
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* Kit
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---
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# Intent
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* Provide an interface for creating families of related or dependent objects without specifying their concrete classes
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---
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# Explanation
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* [Wikipedia](https://en.wikipedia.org/wiki/Abstract_factory_pattern) says:
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> "The abstract factory pattern provides a way to encapsulate a group of individual factories that have a common theme without specifying their concrete classes"
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<br />
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* In plain words:
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* A factory that groups individual but related/dependent factories together without specifying their concrete classes;
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* A factory of factories;
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---
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# Example
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* In a factory that creates kingdoms, we need objects with common theme:
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* Elven kingdom needs an Elven king, Elven castle and Elven army;
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* Orcish kingdom needs an Orcish king, Orcish castle and Orcish army;
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<br />
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* There is a dependency between the objects in the kingdom;
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---
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# Diagram
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* Based on the kingdom example, the diagram below showcases the different concrete factories and their concrete products:
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.center[]
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---
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# Diagram
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* The class diagram below showcases the factory of factories;
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* At runtime, we can define which Kingdom type is needed and pass it as a parameter to define which concrete KingdomFactory to instantiate;
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* The concrete factory returned will then be able to produce the related objects of the specified type;
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.center[]
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---
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# Applicability
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Use the Abstract Factory pattern when:
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* A system should be independent of how its products are created, composed and represented;
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* A system should be configured with one of multiple families of products;
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* A family of related product objects is designed to be used together, and you need to enforce this constraint;
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* You want to provide a class library of products, and you want to reveal just their interfaces, not their implementations;
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---
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# Applicability
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Use the Abstract Factory pattern when:
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* The lifetime of the dependency is conceptually shorter than the lifetime of the consumer;
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* You need a run-time value to construct a particular dependency;
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* You want to decide which product to call from a family at runtime;
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* You need to supply one or more parameters only known at run-time before you can resolve a dependency;
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---
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#Use Cases
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* Selecting to call the appropriate implementation of FileSystemAcmeService or DatabaseAcmeService or NetworkAcmeService at runtime;
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* Unit test case writing becomes much easier;
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---
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# Consequences
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* Dependency injection in java hides the service class dependencies that can lead to runtime errors that would have been caught at compile time
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---
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# Real world examples
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[javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
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[javax.xml.transform.TransformerFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/transform/TransformerFactory.html#newInstance--)
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[javax.xml.xpath.XPathFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/xpath/XPathFactory.html#newInstance--)
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---
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# Credits
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* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
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---
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# Tutorials
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* Source code http://java-design-patterns.com/patterns/abstract-factory/
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